What did Argus Filch's cat do while at Hogwarts How did she help Filch out?

Mrs. Norris

Ms.Norris :)

Filch's cat is a Maine Coon. You can tell because of the M on Mrs. Norris's forehead, which is a feature that all Maine Coons have.

Argus=giant in Greek mythology, a watchman with a hundred sets of eyes (200 in total). Filch=English slang "to steal."

No, but it is possible that he left Hogwarts after the battle